/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_correlate_opt_q15.c
*
* Description:	Correlation of Q15 sequences.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.11 2011/10/18
*    Bug Fix in conv, correlation, partial convolution.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
*
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup Corr
 * @{
 */

/**
 * @brief Correlation of Q15 sequences.
 * @param[in] *pSrcA points to the first input sequence.
 * @param[in] srcALen length of the first input sequence.
 * @param[in] *pSrcB points to the second input sequence.
 * @param[in] srcBLen length of the second input sequence.
 * @param[out] *pDst points to the location where the output result is written.  Length 2 * max(srcALen, srcBLen) - 1.
 * @param[in]  *pScratch points to scratch buffer of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.
 * @return none.
 *
 * \par Restrictions
 *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
 *	In this case input, output, scratch buffers should be aligned by 32-bit
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both inputs are in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * This approach provides 33 guard bits and there is no risk of overflow.
 * The 34.30 result is then truncated to 34.15 format by discarding the low 15 bits and then saturated to 1.15 format.
 *
 * \par
 * Refer to <code>arm_correlate_fast_q15()</code> for a faster but less precise version of this function for Cortex-M3 and Cortex-M4.
 *
 *
 */


void arm_correlate_opt_q15(
    q15_t* pSrcA,
    uint32_t srcALen,
    q15_t* pSrcB,
    uint32_t srcBLen,
    q15_t* pDst,
    q15_t* pScratch)
{
	q15_t* pIn1;                                   /* inputA pointer               */
	q15_t* pIn2;                                   /* inputB pointer               */
	q63_t acc0, acc1, acc2, acc3;                  /* Accumulators                  */
	q15_t* py;                                     /* Intermediate inputB pointer  */
	q31_t x1, x2, x3;                              /* temporary variables for holding input1 and input2 values */
	uint32_t j, blkCnt, outBlockSize;              /* loop counter                 */
	int32_t inc = 1;                               /* output pointer increment     */
	uint32_t tapCnt;
	q31_t y1, y2;
	q15_t* pScr;                                   /* Intermediate pointers        */
	q15_t* pOut = pDst;                            /* output pointer               */
#ifdef UNALIGNED_SUPPORT_DISABLE

	q15_t a, b;

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

	/* The algorithm implementation is based on the lengths of the inputs. */
	/* srcB is always made to slide across srcA. */
	/* So srcBLen is always considered as shorter or equal to srcALen */
	/* But CORR(x, y) is reverse of CORR(y, x) */
	/* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */
	/* and the destination pointer modifier, inc is set to -1 */
	/* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */
	/* But to improve the performance,
	 * we include zeroes in the output instead of zero padding either of the the inputs*/
	/* If srcALen > srcBLen,
	 * (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */
	/* If srcALen < srcBLen,
	 * (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */
	if(srcALen >= srcBLen) {
		/* Initialization of inputA pointer */
		pIn1 = (pSrcA);

		/* Initialization of inputB pointer */
		pIn2 = (pSrcB);

		/* Number of output samples is calculated */
		outBlockSize = (2u * srcALen) - 1u;

		/* When srcALen > srcBLen, zero padding is done to srcB
		 * to make their lengths equal.
		 * Instead, (outBlockSize - (srcALen + srcBLen - 1))
		 * number of output samples are made zero */
		j = outBlockSize - (srcALen + (srcBLen - 1u));

		/* Updating the pointer position to non zero value */
		pOut += j;

	} else {
		/* Initialization of inputA pointer */
		pIn1 = (pSrcB);

		/* Initialization of inputB pointer */
		pIn2 = (pSrcA);

		/* srcBLen is always considered as shorter or equal to srcALen */
		j = srcBLen;
		srcBLen = srcALen;
		srcALen = j;

		/* CORR(x, y) = Reverse order(CORR(y, x)) */
		/* Hence set the destination pointer to point to the last output sample */
		pOut = pDst + ((srcALen + srcBLen) - 2u);

		/* Destination address modifier is set to -1 */
		inc = -1;

	}

	pScr = pScratch;

	/* Fill (srcBLen - 1u) zeros in scratch buffer */
	arm_fill_q15(0, pScr, (srcBLen - 1u));

	/* Update temporary scratch pointer */
	pScr += (srcBLen - 1u);

#ifndef UNALIGNED_SUPPORT_DISABLE

	/* Copy (srcALen) samples in scratch buffer */
	arm_copy_q15(pIn1, pScr, srcALen);

	/* Update pointers */
	//pIn1 += srcALen;
	pScr += srcALen;

#else

	/* Apply loop unrolling and do 4 Copies simultaneously. */
	j = srcALen >> 2u;

	/* First part of the processing with loop unrolling copies 4 data points at a time.
	 ** a second loop below copies for the remaining 1 to 3 samples. */
	while(j > 0u) {
		/* copy second buffer in reversal manner */
		*pScr++ = *pIn1++;
		*pScr++ = *pIn1++;
		*pScr++ = *pIn1++;
		*pScr++ = *pIn1++;

		/* Decrement the loop counter */
		j--;
	}

	/* If the count is not a multiple of 4, copy remaining samples here.
	 ** No loop unrolling is used. */
	j = srcALen % 0x4u;

	while(j > 0u) {
		/* copy second buffer in reversal manner for remaining samples */
		*pScr++ = *pIn1++;

		/* Decrement the loop counter */
		j--;
	}

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

#ifndef UNALIGNED_SUPPORT_DISABLE

	/* Fill (srcBLen - 1u) zeros at end of scratch buffer */
	arm_fill_q15(0, pScr, (srcBLen - 1u));

	/* Update pointer */
	pScr += (srcBLen - 1u);

#else

	/* Apply loop unrolling and do 4 Copies simultaneously. */
	j = (srcBLen - 1u) >> 2u;

	/* First part of the processing with loop unrolling copies 4 data points at a time.
	 ** a second loop below copies for the remaining 1 to 3 samples. */
	while(j > 0u) {
		/* copy second buffer in reversal manner */
		*pScr++ = 0;
		*pScr++ = 0;
		*pScr++ = 0;
		*pScr++ = 0;

		/* Decrement the loop counter */
		j--;
	}

	/* If the count is not a multiple of 4, copy remaining samples here.
	 ** No loop unrolling is used. */
	j = (srcBLen - 1u) % 0x4u;

	while(j > 0u) {
		/* copy second buffer in reversal manner for remaining samples */
		*pScr++ = 0;

		/* Decrement the loop counter */
		j--;
	}

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

	/* Temporary pointer for scratch2 */
	py = pIn2;


	/* Actual correlation process starts here */
	blkCnt = (srcALen + srcBLen - 1u) >> 2;

	while(blkCnt > 0) {
		/* Initialze temporary scratch pointer as scratch1 */
		pScr = pScratch;

		/* Clear Accumlators */
		acc0 = 0;
		acc1 = 0;
		acc2 = 0;
		acc3 = 0;

		/* Read four samples from scratch1 buffer */
		x1 = *__SIMD32(pScr)++;

		/* Read next four samples from scratch1 buffer */
		x2 = *__SIMD32(pScr)++;

		tapCnt = (srcBLen) >> 2u;

		while(tapCnt > 0u) {

#ifndef UNALIGNED_SUPPORT_DISABLE

			/* Read four samples from smaller buffer */
			y1 = _SIMD32_OFFSET(pIn2);
			y2 = _SIMD32_OFFSET(pIn2 + 2u);

			acc0 = __SMLALD(x1, y1, acc0);

			acc2 = __SMLALD(x2, y1, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			acc1 = __SMLALDX(x3, y1, acc1);

			x1 = _SIMD32_OFFSET(pScr);

			acc0 = __SMLALD(x2, y2, acc0);

			acc2 = __SMLALD(x1, y2, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x1, x2, 0);
#else
			x3 = __PKHBT(x2, x1, 0);
#endif

			acc3 = __SMLALDX(x3, y1, acc3);

			acc1 = __SMLALDX(x3, y2, acc1);

			x2 = _SIMD32_OFFSET(pScr + 2u);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			acc3 = __SMLALDX(x3, y2, acc3);

#else

			/* Read four samples from smaller buffer */
			a = *pIn2;
			b = *(pIn2 + 1);

#ifndef ARM_MATH_BIG_ENDIAN
			y1 = __PKHBT(a, b, 16);
#else
			y1 = __PKHBT(b, a, 16);
#endif

			a = *(pIn2 + 2);
			b = *(pIn2 + 3);
#ifndef ARM_MATH_BIG_ENDIAN
			y2 = __PKHBT(a, b, 16);
#else
			y2 = __PKHBT(b, a, 16);
#endif

			acc0 = __SMLALD(x1, y1, acc0);

			acc2 = __SMLALD(x2, y1, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			acc1 = __SMLALDX(x3, y1, acc1);

			a = *pScr;
			b = *(pScr + 1);

#ifndef ARM_MATH_BIG_ENDIAN
			x1 = __PKHBT(a, b, 16);
#else
			x1 = __PKHBT(b, a, 16);
#endif

			acc0 = __SMLALD(x2, y2, acc0);

			acc2 = __SMLALD(x1, y2, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x1, x2, 0);
#else
			x3 = __PKHBT(x2, x1, 0);
#endif

			acc3 = __SMLALDX(x3, y1, acc3);

			acc1 = __SMLALDX(x3, y2, acc1);

			a = *(pScr + 2);
			b = *(pScr + 3);

#ifndef ARM_MATH_BIG_ENDIAN
			x2 = __PKHBT(a, b, 16);
#else
			x2 = __PKHBT(b, a, 16);
#endif

#ifndef ARM_MATH_BIG_ENDIAN
			x3 = __PKHBT(x2, x1, 0);
#else
			x3 = __PKHBT(x1, x2, 0);
#endif

			acc3 = __SMLALDX(x3, y2, acc3);

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

			pIn2 += 4u;

			pScr += 4u;


			/* Decrement the loop counter */
			tapCnt--;
		}



		/* Update scratch pointer for remaining samples of smaller length sequence */
		pScr -= 4u;


		/* apply same above for remaining samples of smaller length sequence */
		tapCnt = (srcBLen) & 3u;

		while(tapCnt > 0u) {

			/* accumlate the results */
			acc0 += (*pScr++ * *pIn2);
			acc1 += (*pScr++ * *pIn2);
			acc2 += (*pScr++ * *pIn2);
			acc3 += (*pScr++ * *pIn2++);

			pScr -= 3u;

			/* Decrement the loop counter */
			tapCnt--;
		}

		blkCnt--;


		/* Store the results in the accumulators in the destination buffer. */
		*pOut = (__SSAT(acc0 >> 15u, 16));
		pOut += inc;
		*pOut = (__SSAT(acc1 >> 15u, 16));
		pOut += inc;
		*pOut = (__SSAT(acc2 >> 15u, 16));
		pOut += inc;
		*pOut = (__SSAT(acc3 >> 15u, 16));
		pOut += inc;

		/* Initialization of inputB pointer */
		pIn2 = py;

		pScratch += 4u;

	}


	blkCnt = (srcALen + srcBLen - 1u) & 0x3;

	/* Calculate correlation for remaining samples of Bigger length sequence */
	while(blkCnt > 0) {
		/* Initialze temporary scratch pointer as scratch1 */
		pScr = pScratch;

		/* Clear Accumlators */
		acc0 = 0;

		tapCnt = (srcBLen) >> 1u;

		while(tapCnt > 0u) {

			acc0 += (*pScr++ * *pIn2++);
			acc0 += (*pScr++ * *pIn2++);

			/* Decrement the loop counter */
			tapCnt--;
		}

		tapCnt = (srcBLen) & 1u;

		/* apply same above for remaining samples of smaller length sequence */
		while(tapCnt > 0u) {

			/* accumlate the results */
			acc0 += (*pScr++ * *pIn2++);

			/* Decrement the loop counter */
			tapCnt--;
		}

		blkCnt--;

		/* Store the result in the accumulator in the destination buffer. */
		*pOut = (q15_t)(__SSAT((acc0 >> 15), 16));

		pOut += inc;

		/* Initialization of inputB pointer */
		pIn2 = py;

		pScratch += 1u;

	}


}

/**
 * @} end of Corr group
 */
